Kitchen fires in homes often involve cooking fats and oils aflame in an open skillet on a range. Historically, portable fire extinguishers for fighting kitchen fires have used a dry chemical class BC fire extinguishent such as sodium bicarbonate. The basic principle behind dry chemicals in extinguishing cooking fires is to combine the fatty esters in the cooking fat or oil with a metal alkali salt. While such dry chemical class BC fire extinguishents have been effective for fighting cooking fires involving animal fats, they exhibited a significantly reduced effectiveness when used in fighting fires involving lighter vegetable-based cooking oils.
As a result, a new class of fire hazard, termed class K, was identified in view of the unique characteristics associated with such cooking oil fires. In fighting a cooking oil fire with a wet chemical fire extinguishing agent, the delivery of the wet chemical agent must not be so forceful as to disturb the surface of the cooking oil, which could cause hot oil to be splashed out of the skillet and result in spreading of the fire to surrounding surfaces. Discharge nozzles associated with conventional fire extinguishers typically discharge a high impact stream of fire extinguishing fluid that can splash the burning cooking fat or oil unto surrounding surfaces, particularly when used by individuals not trained in fire fighting. Conventional discharge nozzles include a relatively large diameter outlet passageway, typically having an inner diameter of about 10 or 11 millimeters, through which the fire extinguishing fluid is discharged.
International patent application publication PCT/US2007/019009 discloses an aerosol fire extinguisher, stated to be rated for class A, B, C and K fires, wherein the fire extinguishing agent is discharged through an elongated slot-like orifice having a length of about 0.075 inches+/−0.01 inches and a width of about 0.035 inches+/−0.01 inches.